The invention relates to the electronic and optoelectronic arts. It is especially applicable to the packaging of light emitting diodes (LEDs) and will be described with particular reference thereto. However, the invention will also find application in the packaging other electronic and optoelectronic devices, such as photodetectors, signal receivers, vertical cavity surface emitting lasers (VCSELs), photovoltaic devices, and the like.
Light emitting diodes find application in fiber optical communications, lighting applications, display applications, and other applications where a compact, low voltage, rugged, and high efficiency light source is advantageous. In many LED applications, a plurality of LEDs are advantageously arranged into an array or other pre-determined arrangement comprising similar or dissimilar LED types. In lighting or display applications, LEDs emitting in the red, green, and blue regions are preferably closely packed to form a color “pixel” that blends the three colors. In this manner white light can be generated. Altematively, by selectively varying the optical output intensity of the three colored LEDs, a selected color can be generated. An array of such “pixels” can form a color display or an illuminating surface emitting white light, among other applications.
The prior art includes fabrication of LED arrays on-chip. In this approach, semiconductor layers comprising the LEDs are generated on a substrate, usually a semiconductor substrate, and individual LEDs of the array are isolated by etching mesas in the LED layers. This approach is limited in application. The LEDs are typically required to be all of one type. The choice of substrate is limited to those compatible with the semiconductor layer generation method. Many commercial LEDs are formed from III-V compound semiconductor layers, and the substrates which are used for the growth of such layers, typically including GaAs and InP wafers, sapphire substrates, and the like, are often expensive, fragile, and of limited lateral area.
A much more flexible approach is to fabricate discrete LEDs using any convenient method, and then to bond the discrete LEDs to a host substrate to form the LED arrangement thereon. In this manner dissimilar LEDs, such as red, green, and blue LEDs comprised of different material layers, can be advantageously combined. The choice of substrate is greatly expanded. However, the individual LEDs are electrically isolated, so that intricate wire bonding or other electrical interconnecting methods are typically applied to complete the array. Additionally, a different host substrate shape and electrical interconnect pattern is needed for each distinct LED arrangement, which limits the standardization of parts and complicates array manufacturing.
The present invention contemplates an improved modular mounting assembly for forming arrays of LEDs and other components.